1. Field of the Invention
The present invention relates to an image capturing apparatus capable of capturing a moving image and its control method.
2. Description of the Related Art
In recent years, a digital camera that records image data obtained by converting an image signal of an object obtained with a solid-state image sensor such as a CCD into a digital signal into a recording medium, which has a movie capturing function in addition to a general still image capturing function is known. It is known that when movie capturing is performed with an image capturing apparatus using a CCD or a CMOS sensor under a fluorescent light driven with a commercial power supply, brightness fluctuation occurs by frame and/or bright/dark horizontal stripes occur in a frame. The brightness/darkness fluctuation is called flicker which can be reduced by controlling an electronic shutter at a shutter speed of n/100 sec (n is a natural number) with respect to flicker of 50 Hz, and a shutter speed of n/120 sec with respect to flicker of 60 Hz.
On the other hand, some digital cameras with the movie capturing function have a function of arbitrarily selecting a recording size of a movie and a frame rate and a function of changing to a full-screen display or an enlarged display. Further, for appreciation of recorded still images and moving images, such digital camera has a function of playback display on an LCD monitor unit or the like of the camera, and further, appreciation on a TV monitor or the like can be performed through a video output terminal or an HDMI terminal. As the video output mode in this case, the NTSC or PAL system is adopted in the respective regions in the world.
Japanese Patent No. 3823314 discloses extraction of a flicker component upon flicker detection by detection by each of plural flicker detection regions set in a vertical scanning direction and obtaining a difference between brightness data of continuous two regions, then measuring an interval between the extracted flicker components and converting the interval to a frequency. Further, Japanese Patent Laid-Open No. 07-298112 discloses, in a moving image pickup system, freely changing a frame rate upon recording or through operation in accordance with purpose.
In a movie capturing function enabling frame rate selection, it might be difficult to perform flicker detection in control at a selected frame rate. Upon image capturing under a fluorescent light connected to a commercial power supply, brightness/darkness horizontal stripes occur in a recorded moving image. Further, when a recorded moving image is playback-displayed, it is desirable to playback-display the moving image at a frame rate selected upon recording. However, upon appreciation of the moving image on a TV monitor or the like via a video output terminal or an HDMI terminal, it is necessary to perform output at a predetermined frame rate based on standards of the NTSC or PAL system. Accordingly, appreciation is performed at a display frame rate which is different from that upon recording.